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Author Topic: Understanding a custom system  (Read 553 times)
Greenbeast
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« on: September 10, 2017, 07:14:46 PM »

gurus,

I'm looking for some help understanding someone else's custom solid fuel fired central heating/HW system.
My step-brother asked me to look at it as his mother-in-law has been left this system by her late husband (who was a proper bodgineer).

It comprises a rayburn with water jacket, a swimming pool HE, an unvented cylinder and oddly, a converted beer keg which is plumbed in parallel with the rayburn's water circtuit

I think this is a fair representation of the layout.



The lower pipe stat controls the rayburn circuit pump, it also supplies power to the upper stat.
There is a rudimentary controller box containing a 240v relay, and the various connections between pumps, stats and the cylinder cupboard where the motorised valves, cylinder (with stat) and standard honeywell connection box is.
I'm unclear what the upper stat controls but it appears appears to latch the relay on which powers the CH pump (when the top stat goes off the CH pump continues to run until the lower stat goes off which cuts power)

Looking for thoughts on the purpose of the keg, some kind of buffer?
Also the dynamic between the two stats either side of the keg and the likely temps they should be at.

Help much appreciated!!
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biff
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« Reply #1 on: September 10, 2017, 07:31:09 PM »

  Hi GB,
        I suspect that the keg is a thermal store of sorts,
                  Once the fire has died down, the C/H pump switches off but the heat will still rise into the Beer keg. If it is situated in a spot where the householder can benefit from the heat of it,then i may well be right but if it is tucked away in some draughty spot,then it might be a heat leak. In truth, I am only guessing.
                                                                                            Biff
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Greenbeast
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« Reply #2 on: September 10, 2017, 07:38:49 PM »

It is in an insulated cupboard above/behind the rayburn.
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desperate
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« Reply #3 on: September 10, 2017, 07:55:15 PM »

Converted beer keg?? unvented cylinder?? solid fuel boiler?? = Destroy It Yourself DEEESAARRSTER DAAHHLING.

Seriously mate you should consider getting rid of it as it is set up now, your house insurance is invalid and you could well be taking more than a little chance there.

Desp
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Crazy old duffer
Greenbeast
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« Reply #4 on: September 10, 2017, 08:08:10 PM »

nothing to do with me!
Just trying to offer some advice on how to operate it  Smiley

The rayburn circuit is open vented (including the keg)
The cylinder does not get any heat unless the pump runs, so there's no chance of overheating the cylinder.
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desperate
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« Reply #5 on: September 10, 2017, 08:43:03 PM »

Sure mate, I am not implying you installed it or anything, but the best advice is to ditch it. Even if in theory you could make it safe, it seriously contravenes all kinds of regs, anything at all goes wrong in the house and the householders are entirely on their own. Personally would you want to be involved in that? I know I wouldn't.

I know that sounds a bit anally jobsworth and all that, but why anyone would want to cobble something like that together when there are many better ways and possibly cheaper and certainly less risky ways of doing it are beyond me.

Desp
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Countrypaul
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« Reply #6 on: September 10, 2017, 08:49:57 PM »

The pipework schematic you have preesnted doesn't appear to make sense to me. How can you have 3 cold pipes into one junction and a hot supply coming out of it for the CH/HW tank? The way you have laid the pipework out why would the water ever bother to flow though the keg? It would appear that it could just short circuit that and go through the Raburn and pump. Is that upper pump correctly orientated as it appears to be pushing cold water up into the Raburn/keg?

The keg may be a heat dump ie. large enough to absorb the heat from the Raburn when the pumps stop, but the layout of the pipes as shown makes that difficult to explain.
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Greenbeast
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« Reply #7 on: September 10, 2017, 09:02:53 PM »

The pipework schematic you have preesnted doesn't appear to make sense to me. How can you have 3 cold pipes into one junction and a hot supply coming out of it for the CH/HW tank? The way you have laid the pipework out why would the water ever bother to flow though the keg? It would appear that it could just short circuit that and go through the Raburn and pump. Is that upper pump correctly orientated as it appears to be pushing cold water up into the Raburn/keg?

The keg may be a heat dump ie. large enough to absorb the heat from the Raburn when the pumps stop, but the layout of the pipes as shown makes that difficult to explain.

sorry yes i apologise. i was doing this from some note and memory from earlier today.
In reality the rayburn pump does operate in the correct direction, the 'junction should be labeled as the heat exchanger, so it isn't really a junction
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Westie
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« Reply #8 on: September 11, 2017, 11:51:48 AM »

Like Bif said, it's a thermal store.  Leave the  pump on the Rayburn loop running all the time switched by a stat on that loop, so it shuts off when the stove is cold, you can then continue to draw off the heat from the store , via the exchanger to the DHW/CH loop until the store exhausted.  Better make sure you have a decent corrosion inhibitor in the Rayburn loop as the beer barrel is prob Aluminium sh*tfan

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Greenbeast
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« Reply #9 on: September 11, 2017, 12:31:41 PM »

Thanks for your thoughts. What sort of temps should I set the two stats at? Do they just want to be both enough that they trigger shortly after the stove is lit, say 40C?
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Westie
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« Reply #10 on: September 11, 2017, 01:50:40 PM »

Thanks for your thoughts. What sort of temps should I set the two stats at? Do they just want to be both enough that they trigger shortly after the stove is lit, say 40C?


No idea, 40C sounds a bit low to me, think that it's a trial and error setup.  If the tank is above and behind the Rayburn I'm surprised it needs to be pumped, it should thermosiphon  assuming the pipework is a decent diameter? On the other hand a beer keg might be a bit too squat to get a decent enough differential to get it to convect?


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Fintray
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« Reply #11 on: September 11, 2017, 04:09:47 PM »

It looks to me as he has used the beer keg as a buffer so when the Rayburn is lit and heats up, the lower stat switches on the pump circulating the warm water through the heat exchanger back into the Rayburn (a bit like a loading valve to maintain boiler return temperature). Once the water is hot enough causing the top stat to operate the heating pump comes on and it will switch the pumps as and when the water temperature drops.
« Last Edit: September 11, 2017, 04:12:52 PM by Fintray » Logged
Greenbeast
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« Reply #12 on: September 11, 2017, 04:54:33 PM »

It looks to me as he has used the beer keg as a buffer so when the Rayburn is lit and heats up, the lower stat switches on the pump circulating the warm water through the heat exchanger back into the Rayburn (a bit like a loading valve to maintain boiler return temperature). Once the water is hot enough causing the top stat to operate the heating pump comes on and it will switch the pumps as and when the water temperature drops.

This was my first thought to my step brother when he video called me and attempted to walk me through it.
On that basis what temperature to set the stats at?
« Last Edit: September 11, 2017, 10:14:10 PM by Greenbeast » Logged
Fintray
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« Reply #13 on: September 12, 2017, 06:13:22 AM »

You could set the lower one at 40 and the higher one at say 70 as I think the Laddomat units are set at about that, you could try it and see and if it starts to kettle turn the upper stat down a touch.
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Greenbeast
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« Reply #14 on: September 12, 2017, 06:34:53 AM »

Nice one thanks
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